High Refractive Index GRIN Lens for IR Optics

Abstract

Infrared gradient refractive index (GRIN) material lenses have attracted much attention due to their continuously varying refractive index as a function of spatial coordinates in the medium. Herein, a glass accumulation thermal diffusion method was used to fabricate a high refractive index GRIN lens. Six Ge17.2As17.2SexTe(65−x) (x = 10.5–16) glasses with good thermal stability and high refractive index (n@10 μm > 3.1) were selected for thermal diffusion. The refractive index span (∆n) of 0.12 was achieved in this GRIN lens. After thermal diffusion, the lens still had good transmittance (45%) in the range of 8–12 μm. Thermal imaging confirmed that this lens can be molded into the designed shape. The refractive index profile was indirectly characterized by the structure and composition changes. The structure and composition variation became linear with the increase in temperature from 260 °C to 270 °C for 12 h, indicating that the refractive index changed linearly along the axis. The GRIN lens with a high refractive index could find applications in infrared optical systems and infrared lenses for thermal imaging.

Infrared Gradient Refractive INdex (GRIN) Materials Through Fast Solid‐Solid Na+/Ag+ Ionic Exchange in Chalco‐Halide Glasses

“…Nowadays, no commercial solution exists for such lenses, due to the difficulty of creating index gradient with good precision, stability, and reproducibility. Many ways of fabricating those GRIN materials have been studied lately in chalcogenide glasses, as glass interlayer element diffusion, [7][8][9][10] controlled crystallization, [11][12][13] laser physicochemical modifications, [14][15][16] electrospray printing, [17] or thermal poling. [18] In most cases, axial GRIN was considered, as radial GRIN is generally still more difficult to obtain.…”

Modeling and admittance recursive simulation of anti-reflective coatings for photothermal conversion: synergy between subwavelength structures and gradient refractive index layers

“…Among various anti-reflective coatings, subwavelength structures 17–22 and gradient refractive layers 23–27 are currently widely used. Hong Li et al 28 prepared PiTG with a GRIN coating, revealing that compared to single refractive index (SRIN) coatings, the luminous efficiency of PiTG with the GRIN coating increased from 9.51% to 23.12%.…”